Matthews' first book was Wa'kon-tah: The Osage and The White Man's Road (1929), which was a Book-of-the-Month Club bestseller.

His most famous work is Sundown (1934), his only novel. It is a semi-autobiographicial novel about a young Osage, Challenge "Chal" Windzer. After leaving home to study at the University of Oklahoma and having served in the military, Chal no longer feels at home when he returns to his tribal community. The novel portrays Chal's feelings of alienation and hopelessness as his life takes a downward turn. The novel is set against the backdrop of the oil boom that took place in on Osage land in Oklahoma in the 1900s and 1910s, and depicts the frictions within the tribal community which resulted from this bonanza.